A genetic disorder that affects the ability of the body to effectively break down fat from our diet. It is typically characterized by hypotonia (low muscle tone) and seizures in the newborn period. Other symptoms include unusual facial features and an enlarged liver (hepatomegaly). Most babies with this condition nevergain anydevelopmental skills and do not survive past the age of 2. DBP deficiency is caused by mutations in the HSD17B4 gene and is inherited in an autosomal recessive manner. Some researchers have suggested classifying DBP deficiency into three subtypes, depending on how severely the mutation in the HSD17B4 gene affects the function of the gene and the protein that it codes for. Almost all individuals with types I, II, and III have similar signs and symptoms. A fourth subtype has additionally been proposed for individuals that have less severe symptoms. While there is no cure for DBP deficiency, treatment is focused on improving nutrition and growth, controlling symptoms, and limiting the progression of liver disease. The disease is d-bifunctional protein deficiency (MONDO_0009855). Also known as: D-bifunctional enzyme deficiency, HSD17B4 deficiency, multifunctional enzyme deficiency, peroxisomal multifunctional enzyme (MFE2) deficiency, peroxisomal multifunctional enzyme deficiency, pseudo-Zellweger syndrome.